/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package scw.util.task.support;

import java.util.concurrent.Callable;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
import java.util.concurrent.RejectedExecutionException;

import scw.core.Assert;
import scw.util.concurrent.ListenableFuture;
import scw.util.concurrent.ListenableFutureTask;
import scw.util.task.AsyncListenableTaskExecutor;
import scw.util.task.TaskDecorator;
import scw.util.task.TaskRejectedException;

/**
 * Adapter that takes a JDK {@code java.util.concurrent.Executor} and exposes a
 * Spring {@link org.springframework.core.task.TaskExecutor} for it. Also
 * detects an extended {@code java.util.concurrent.ExecutorService}, adapting
 * the {@link org.springframework.core.task.AsyncTaskExecutor} interface
 * accordingly.
 *
 * @author Juergen Hoeller
 * @see java.util.concurrent.Executor
 * @see java.util.concurrent.ExecutorService
 * @see java.util.concurrent.Executors
 */
public class TaskExecutorAdapter implements AsyncListenableTaskExecutor {

	private final Executor concurrentExecutor;

	private TaskDecorator taskDecorator;

	/**
	 * Create a new TaskExecutorAdapter, using the given JDK concurrent
	 * executor.
	 * 
	 * @param concurrentExecutor
	 *            the JDK concurrent executor to delegate to
	 */
	public TaskExecutorAdapter(Executor concurrentExecutor) {
		Assert.notNull(concurrentExecutor, "Executor must not be null");
		this.concurrentExecutor = concurrentExecutor;
	}

	/**
	 * Specify a custom {@link TaskDecorator} to be applied to any
	 * {@link Runnable} about to be executed.
	 * <p>
	 * Note that such a decorator is not necessarily being applied to the
	 * user-supplied {@code Runnable}/{@code Callable} but rather to the actual
	 * execution callback (which may be a wrapper around the user-supplied
	 * task).
	 * <p>
	 * The primary use case is to set some execution context around the task's
	 * invocation, or to provide some monitoring/statistics for task execution.
	 * 
	 */
	public final void setTaskDecorator(TaskDecorator taskDecorator) {
		this.taskDecorator = taskDecorator;
	}

	/**
	 * Delegates to the specified JDK concurrent executor.
	 * 
	 * @see java.util.concurrent.Executor#execute(Runnable)
	 */
	public void execute(Runnable task) {
		try {
			doExecute(this.concurrentExecutor, this.taskDecorator, task);
		} catch (RejectedExecutionException ex) {
			throw new TaskRejectedException("Executor [" + this.concurrentExecutor + "] did not accept task: " + task,
					ex);
		}
	}

	public void execute(Runnable task, long startTimeout) {
		execute(task);
	}

	public Future<?> submit(Runnable task) {
		try {
			if (this.taskDecorator == null && this.concurrentExecutor instanceof ExecutorService) {
				return ((ExecutorService) this.concurrentExecutor).submit(task);
			} else {
				FutureTask<Object> future = new FutureTask<Object>(task, null);
				doExecute(this.concurrentExecutor, this.taskDecorator, future);
				return future;
			}
		} catch (RejectedExecutionException ex) {
			throw new TaskRejectedException("Executor [" + this.concurrentExecutor + "] did not accept task: " + task,
					ex);
		}
	}

	public <T> Future<T> submit(Callable<T> task) {
		try {
			if (this.taskDecorator == null && this.concurrentExecutor instanceof ExecutorService) {
				return ((ExecutorService) this.concurrentExecutor).submit(task);
			} else {
				FutureTask<T> future = new FutureTask<T>(task);
				doExecute(this.concurrentExecutor, this.taskDecorator, future);
				return future;
			}
		} catch (RejectedExecutionException ex) {
			throw new TaskRejectedException("Executor [" + this.concurrentExecutor + "] did not accept task: " + task,
					ex);
		}
	}

	public ListenableFuture<?> submitListenable(Runnable task) {
		try {
			ListenableFutureTask<Object> future = new ListenableFutureTask<Object>(task, null);
			doExecute(this.concurrentExecutor, this.taskDecorator, future);
			return future;
		} catch (RejectedExecutionException ex) {
			throw new TaskRejectedException("Executor [" + this.concurrentExecutor + "] did not accept task: " + task,
					ex);
		}
	}

	public <T> ListenableFuture<T> submitListenable(Callable<T> task) {
		try {
			ListenableFutureTask<T> future = new ListenableFutureTask<T>(task);
			doExecute(this.concurrentExecutor, this.taskDecorator, future);
			return future;
		} catch (RejectedExecutionException ex) {
			throw new TaskRejectedException("Executor [" + this.concurrentExecutor + "] did not accept task: " + task,
					ex);
		}
	}

	/**
	 * Actually execute the given {@code Runnable} (which may be a user-supplied
	 * task or a wrapper around a user-supplied task) with the given executor.
	 * 
	 * @param concurrentExecutor
	 *            the underlying JDK concurrent executor to delegate to
	 * @param taskDecorator
	 *            the specified decorator to be applied, if any
	 * @param runnable
	 *            the runnable to execute
	 * @throws RejectedExecutionException
	 *             if the given runnable cannot be accepted
	 */
	protected void doExecute(Executor concurrentExecutor, TaskDecorator taskDecorator, Runnable runnable)
			throws RejectedExecutionException {

		concurrentExecutor.execute(taskDecorator != null ? taskDecorator.decorate(runnable) : runnable);
	}

}
